Memory is one type of integrated circuitry, and is used in electronic systems for storing data. Integrated memory is usually fabricated in one or more arrays of individual memory cells. The memory cells are configured to retain or store memory in at least two different selectable states. In a binary system, the states are considered as either a “0” or a “1”. In other systems, at least some individual memory cells may be configured to store more than two levels or states of information.
One type of memory is phase change memory (PCM). Such memory utilizes phase change material as a programmable material. Example phase change materials that may be utilized in PCM are chalcogenide materials.
The phase change material reversibly transforms from one phase to another through application of appropriate stimulus. Each phase may be utilized as a memory state, and thus an individual PCM cell may have two selectable memory states that correspond to two inducible phases of the phase change material.
A difficulty that may be encountered during utilization of PCM is described with reference to FIGS. 1 and 2. FIG. 1 shows a portion of a construction 10 comprising a PCM array. The array comprises memory cells 12-14, with each memory cell comprising phase change material 15. The phase change material is provided between a heater material 16 and an electrically conductive capping material 18. A bitline 20 extends across the memory cells 12-14, and is electrically coupled to the memory cells through the capping material 18. The memory cells are also electrically coupled to wordlines 22-24 that extend under the memory cells.
The illustrated memory cells 12-14 may be along a single column of the memory array, and accordingly are connected to a common bitline.
The wordlines may extend in and out of the page relative to the cross-sectional view of FIG. 1, and may connect the illustrated memory cells with other memory cells (not shown) along rows of the memory array.
Electrically insulative material 26 is provided between the memory cells. The electrically insulative material may comprise a single composition (as shown), or may comprise multiple different compositions.
Referring to FIG. 2, memory cell 13 may be selectively programmed through appropriate electrical stimulus along bitline 20 and wordline 23. Such programming may involve utilizing heater material 16 to raise a temperature of programmable material 15 to at least about a transition temperature suitable to alter crystallinity within material 15. Such temperature raise creates a region 28 within the programmable material of memory cell 13 having altered physical properties, and thus transitions the memory cell to a different memory state than the adjacent memory cells 12 and 14.
A problem that may occur during the programming of memory cell 13 is thermal crosstalk between memory cell 13 and the adjacent memory cells 12 and 14. Arrows 29 are provided to diagrammatically illustrate thermal energy migrating outwardly from memory cell 13 during the programming of such memory cell. The thermal crosstalk may cause a so-called “program-disturb” phenomena in which data is lost from a memory cell during programming of a neighboring memory cell.
It would be desirable to alleviate or prevent thermal crosstalk between neighboring memory cells of PCM arrays.